1. Field of the Invention
This invention relates to binder-containing colloidal aqueous organopolysiloxane dispersions and their use for treating fiber-type and sheet-type substrates, more particularly fiber-type substrates of natural and/or synthetic origin, and in particular, textile floor coverings such as carpets and carpet flooring.
2. Description of the Related Art
Organopolysiloxane hydrosols are well known and processes for making them are described for example in U.S. Pat. Nos. 3,433,780, 4,857,582 (corresponding to DE 37 17 075 A1) and U.S. Pat. No. 5,281,657 (corresponding to EP 492 377 A2).
Similarly, uses of organopolysiloxane hydrosols as impregnating and coating agents are known. DE 1 594 985 A claims the use for treating natural and synthetic fiber materials. It is specifically stated that carpet products exhibit improved dry soil repellency following impregnation with colloidal suspensions of organosilsesquioxanes.
DE 30 04 824 A1 selects colloidal suspensions of organosilsesquioxanes in conjunction with silica hydrosols for pile stabilization of textile materials. However, films of organosilsesquioxanes prove to be hard and brittle; i.e., coatings of organosilsesquioxanes on flexibly bendable and wrinkable substrates tend to be frangible and are easily detachable in particulate form by mechanical stress.
For this reason, organopolysilsesquioxanes are generally used together with binder materials. For reasons of water- and oil-repellent properties, binders in the textile sector usually comprise fluorocarbon-containing systems. U.S. Pat. No. 6,225,403 relates to a composition and method for treating textile substrates to impart oil, water and soil repellency. To this end, less than 1% of fluorocarbon resins are used together with, for example, up to 10% of organosilisesquioxane copolymer particles in the form of a hydrosol. Such mixing ratios are unlikely to provide sufficient adherence to the substrate. Frequently there is a desire nowadays, born out of the environmental debate and the possible persistence of fluorocarbon in the human body, for binder systems containing no perfluorocarbons.
Fluorocarbon-free binder systems for organosilsesquioxanes are likewise repeatedly found in the patent literature.
For instance, US 2003/0099844 A1 describes a coating composition for producing an insulating film, comprising alkoxysilanes and/or their hydrolyzates, an organic polymer, water, alcohol and optionally an organic solubilizer. The organic polymer may be inter alia a polyvinyl alcohol or polyvinyl ester. Polyvinyl alcohol used as a protective colloid for stabilizing organopolysiloxane hydrosols is also mentioned in the above-cited U.S. Pat. No. 5,281,657 (corresponding to EP 492 377 A2).
In “Preparation and properties of poly(vinyl alcohol)/silica nanocomposites derived from copolymerization of vinyl silica nanoparticles and vinyl acetate”, Xin Jia et al., European Polymer Journal 43 (2007), pages 1123-1131, preparation of nanocomposites is described. The synthesis proceeds via the route of a free-radical in situ copolymerization of vinyl-containing silicas with vinyl acetate. Subsequent saponification gives rise to filmable polyvinyl alcohols which, owing to their content of covalently bonded silicone particles, have improved mechanical and thermal stabilities. The proportion of silica particles in the nanocomposites is up to max. 4% by weight. Soil-repellent properties are unlikely for a coating with such materials.
Silane-containing organic polymers are also known from the literature. Usually, they are produced via the free-radical copolymerization of olefinic organic monomer with olefinically functionalized silanes. Especially vinyl acetate or vinyl alcohol copolymers are obtainable in this way. Examples thereof are found in EP 76 490 A1, US 2004/0014857 A (corresponding to EP 1 382 621 A1) and DE 10 2005 054 913 A1.
Coatings with silane-containing vinyl acetate or vinyl alcohol copolymers exhibit good film quality and substrate adherence, but no soil-repellent properties of the kind known from coatings of organopolysiloxane hydrosols.
Yet combining organopolysiloxane hydrosols with suitable fluorocarbon-free organic binders in order to achieve good soil-repellent effects on fibrous substrates coupled with good film quality is problematic. This is because in practice it is found that only few organic binder formulations are compatible with organopolysiloxane hydrosols, i.e., do not lead to gelling with organopolysiloxane hydrosols. Good film quality and adherence of the organopolysiloxane hydrosol then requires the addition of so much binder that no or substantially impaired soil-repellent effects are to be seen.